Catheters are flexible medical instruments for use in the introduction and withdrawal of fluids to and from body cavities, ducts and vessels. Catheters are used for many different applications within the human body including the administration of liquid therapeutic agents and the removal of bodily fluids for testing, monitoring, treatment or disposal. Catheters have a particular application in hemodialysis procedures, in which blood is withdrawn from a blood vessel, directed to a hemodialysis unit for dialysis or purification, and subsequently returned to the blood vessel.
Typically, chronic catheters remain implanted within the body for extended periods of time. Because of this, clotting and thrombus formation within the catheter lumen or lumens can be problematic. To minimize the potential problems which may result from thrombus formation within the catheter lumen(s), it is common to “lock” the catheter during periods of non-use, such as an interdialytic period. Locking typically involves flushing the catheter with saline to remove blood and other fluids from the catheter lumen(s) and injecting an anticoagulant solution, for example, heparin, into the catheter to fill the lumen(s). The anticoagulant solution displaces any blood that may remain in the lumen(s) and actively inhibits thrombus formation within the lumen(s) of the catheter.
One problem associated with known catheters is that during periods of non-use, such as the interdialytic period, the anticoagulant in the distal end of the catheter lumen tends to partially drain from the lumen such that blood is able to enter the distal end of the catheter. This stagnant blood within the distal end of the catheter results in thrombus formation at the distal end of the catheter lumen.
It would be desirable to provide a catheter that is configured to retain an anticoagulant within the catheter lumen(s) during the periods of non-use to prevent thrombus formation within the catheter. It would also be desirable to provide a catheter that is configured to prevent the inflow of blood into the catheter lumen(s) during periods of non-use to prevent thrombosis formation without the use of a locking solution, such as heparin.